I am a massive train geek, so when I saw this game in PC World a few years back, I just had to have it.
It's like setting up a model railroad in your own house, but without the hassle of hammering and decorating it all by yourself. However, as this is a Sid Meier game, there are set boundaries as to what you can and cannot do. The game usually has to be played with one of the many scenarios, meaning that there are set goals to reach. You can, however, make custom maps that can be shared- a touch that came in with patch 1.1.
Depending on the setting you choose, the graphics change dramatically- however, they always remain steadily good and therefore this doesn't distract from the gameplay at all.
This game plays quite simply, using a few set ways of winning the game as the main thing that keeps you interested. If you're into trains, it's a fun little game to pick up and play, especially when the internet is down, but if you get bored of the game's "do these tasks by this date or else... well, we won't actually do anything to you" style, I'd suggest leaving it for a little while, otherwise the game will just grate on you.
Scenarios are the main way of playing the game, with a semi "sandbox" style being introduced later. The scenarios are truly challenging and can lead to rage-quitting the game on multiple occasions and having to start again. However, once you get the hang of it the scenarios are OK and you can whizz through the game if that's the way you choose to play it.
There is a multiplayer option, where you play one of the scenarios (or a player-made map) against other people instead of AIs. The people playing this game are quite good at it, by the way XD
I love this game, but on full settings on my old PC the game ran very slowly, sometimes even crashing. So if you're going to play it, I suggest you have a computer with WAY more than the minimum specs. It's good fun!